Currently, portable articulated arms are provided as a measurement system with a host computer and applications software. The articulated arm is commonly used to measure points on an object and these measured points are compared to computer aided design (CAD) data stored on the host computer to determine if the object is within the CAD specification. In other words, the CAD data is the reference data to which actual measurements made by the articulated arm are compared. The host computer may also contain applications software that guides the operator through the inspection process. For many situations involving complicated applications, this arrangement is appropriate since the user will observe the three-dimensional CAD data on the host computer while responding to complex commands in the applications software.
An example of a prior art portable CMM for use in the above-discussed measurement system is disclosed in U.S. Pat. No. 5,402,582 ('582), which is assigned to the assignee hereof and incorporated herein by reference. The '582 patent discloses a conventional three-dimensional measuring system composed of a manually operated multi-jointed articulated arm having a support base on one end thereof and a measurement probe at the other end. A host computer communicates with the arm via an intermediate controller or serial box. It will be appreciated that in the '582 patent, the arm will electronically communicate with the serial box which, in turn, electronically communicates with the host computer. Commonly assigned U.S. Pat. No. 5,611,147 ('147), which is again incorporated herein by reference, discloses a similar CMM having an articulated arm. In this patent, the articulated arm includes a number of important features including an additional rotational axis at the probe end thus providing for an arm with either a two-one-three or a two-two-three joint configuration (the latter case being a 7 axis arm) as well as improved pre-loaded bearing constructions for the bearings in the arm.
More current portable CMMs of the type described herein do not necessitate the use of an intermediate controller or serial box since the functionality thereof is now incorporated in the software provided by the host computer. For example, commonly assigned U.S. Pat. No. 5,978,748 ('748), which is incorporated herein by reference, discloses an articulated arm having an on-board controller which stores one or more executable programs and which provides the user with instructions (e.g., inspection procedures) and stores the CAD-data that serves as the reference data. In the '748 patent, a controller is mounted to the arm and runs the executable program which directs the user through a process such as an inspection procedure. U.S. Pat. No. 6,612,044 assigned to the assignee hereof and incorporated herein by reference, discloses a method and system for delivering executable programs to users of coordinate measurement systems of the type disclosed in the '748 patent.
Commonly assigned U.S. Pat. No. 6,131,299 ('299), (all the contents of which is incorporated herein by reference), discloses an articulated arm having a display device positioned thereon to allow an operator to have a convenient display of positional data and system menu prompts. U.S. Pat. No. 6,219,928 ('928), which is assigned to the assignee and incorporated herein by reference, discloses a serial network for the articulated arm. The serial network communicates data from transducers located in the arm to a controller. Each transducer includes a transducer interface having a memory which stores transducer data. The controller serially addresses each memory and the data is transferred from the transducer interface memory to the controller.
U.S. Pat. No. 6,957,496, assigned to the assignee hereof and incorporated herein by reference, discloses a portable CMM which comprises an articulated arm having jointed arm segments. In one embodiment, the arm segments include bearing/encoder cartridges which are attached to each other at predetermined angles. Each cartridge contains at least one, and preferably two, preloaded bearing assemblies and an encoder, preferably an optical encoder, all assembled in a housing. Preferably, two or more encoder read heads are used in each joint so as to improve measurement accuracy.
U.S. Pat. No. 7,073,271, assigned to the assignee hereof and incorporated herein by reference, also discloses an articulated arm-type CMM having jointed arm segments. The jointed arm segments include a rotatable shaft, at least two spaced bearings and a housing surrounding the bearings and shaft wherein races for the bearings are formed by at least one of the following: (1) the shaft constitutes the inner race of at least one of the two bearings and (2)the housing constitutes the outer race of at least one of the two bearings.
U.S. Pat. No. 7,050,930, assigned to the assignee hereof and incorporated herein by reference, discloses an articulated arm-type CMM wherein the articulated arm includes a measurement probe having a laser scanner rotatably mounted thereon.
While well suited for their intended purposes, there is a continued and perceived need in the industry for improved portable CMMs that are easier to use, more efficient to manufacture, provide improved features and can be sold at a lower cost.